Method of making stretch yarns and fabrics



Jan. 30, 1968 J. 5 BROWN ETAL 3.365.759

METHOD OF MAKING STRETCH YARNS AND FABRICS I Filed July 22, 1965MULTI-PLY CELLULOSE YARN TREAT WITH SWELLING AGENT UNDER CONTROLLEDTENSION- F/ 6- POTENTIALLY STRETCHY YARN REVERSE TWIST STRETCHY,BULKYIRREGULAR YARN MULTI-PLY CELLULOSE YARN TREAT WITH SWELLING AGENT UNDERCONTROLLED TENSION POTENTIALLY,STRETCHY YARN REVERSE TWIST STRETCHY,BULKY, IRREGULAR YAR N PULL OUT EXTENDED YARN WEAVING, KNITTING, ETC.

FABRIC RELAX WITH WATER OR STEAM STRE TCH FABRIC lnven/ors James E.Brown Wi/l/am fi'an/r Toy/0r F/ G 3 By Meir attorneys mm! K UnitedStates Patent i 3,365,769 METHOD OF MAKING STRETCH YARYS AND FABRICSJames E. Brown, Axis, Ala., and William Frank Taylor, Chester, Va.,assignors to Courtanlds North America Inc., New York, N.Y., acorporation of Alabama Filed July 22, 1965, Ser. No. 474,033 6 Claims.(Cl. 28-76) This invention relates to a method for making stretch yarnsand fabrics from cellulose filaments.

The use of stretchy yarns to make fabrics which have stretch propertieshas become increasingly widespread. Most of such yarns contain anelastomeric material, either as a component fiber or as an impregnant.The use of elastomers has drawbacks because in many instances theyimpart an undesirable hand or feel to the fabric and because they add tothe cost of the fabric. Moreover, it stretch is imparted to the yarnbefore it is made into fabric, it becomes difiicult to handle the yarnon conventional textile machinery.

There is therefore a need for an inexpensive yarn which will havestretch properties, and which can be processed on conventional textilemachinery.

In our copending application Ser. No. 363,248, filed Apr. 28, 1964,there is described a process in which stretch yarns and fabrics can bemade from cellulosic filamentary material. In this prior process amulti-ply yarn is treated with a swelling agent for cellulose in thesubstantial absence of tension and then reverse twisted.

The yarns obtained under the conditions described in I ,said priorapplication have excellent properties, but because the process describedrequires treatment in the absence of tension, it cannot conveniently bepracticed in many types of conventional textile apparatus whichinherently require that the yarn be subjected to tension duringprocessing.

It has now been found that a satisfactory yarn having good stretchproperties can be made when the yarn is treated under tension, providedthat the amount of tension applied is restricted to that which willmaintain the yarn at from about 50 to 100% of its original, untreatedlength; or stated another way, which will give a yield, in terms of yarnlength, of 50 to 100%.

The invention therefore includes a method for making a stretchy yarnwhich comprises contacting a cellulose yarn having at least two plieswith a cellulose swelling agent equivalent to an aqueous solutioncontaining to 40% sodium hydroxide and capable of shrinking said yarn,maintaining said yarn during contact with said swelling agent undertension sufiicient to maintain said yarn at at least 50% of its originallength and subsequently reverse twisting the treated yarn.

Yarn made in accordance with the invention has an irregular appearance,as will be described more fully below. It may be drawn out and ifretained in an extended position for a period of time, will lose itsstretchy characteristics. In this condition it may be used on textilemachinery like any non-stretch yarn, to make woven or knitted fabrics.Such fabrics upon being wetted out or steamed, without tension, willdevelop the stretch characteristics originally present in the yarn.

In another aspect the invention therefore includes a method for making astretch fabric which comprises treating a multi-ply yarn consistingessentially of cellulose filaments with a swelling agent for cellulose,equivalent to an aqueous solution containing between about 3,365,769Patented Jan. 30, 1963 5% and about 40% NaOH and capable of shrinkingsaid yarn, under a tension suldcient to maintain said yarn at at least50% its original length, drying the yarn, releasing said tension,reverse twisting the yarn ".0 prc duce a coiled yarn having anirregular, three-dimensional series of helical sections, pulling out theyarn to form a substantially straight yarn, converting the straight yarnto fabric and relaxing the fabric in an aqueous fluid.

In the drawings:

FIG. 1 is a flow diagram, illustrating the manufacture of stretch yarnin accordance with the invention.

FIG. 2 is a flow diagram illustrating the manufacture of stretch fabricin accordance with the invention.

FIG. 3 is a view in elevation of reverse twisted yarn made according tothe invention.

Referring first to FIG. 1, yarn in accordance with the invention is madeby treating a multi-ply yarn consisting essentially of cellulose fiberswith a swelling agent for cellulose.

The multi-ply yarn used in the invention has at least two plies and mayhave up to say 6 plies. The individual filaments making up the singlesyarns may be staple filaments, or continuous filaments. The filamentsmay be made from natural cellulose, e.g. cotton, ramie, jute and linen;or they may be synthetic filaments, i.e., rayon whether made by theviscose, cuprammonium or nitrate processes, or by the saponification oforganic esters of cellulose such as cellulose acetate. Best results havebeen obtained with so-called high wet modulus or poly nosique viscoserayon. This is a relatively new type of rayon made by extrudingunripened viscose into a coagulating bath having little regenerativepower. and stretching the resulting filaments to a high degree whilethey are still substantially unregenerated. Such processes are describedin the United States patents to Tackikawa, 2,732,279, and, Cox,2,937,070.

Fiber made in this way has a fine and stable microfibrillar structure, asmooth, non-crenulated skin, a generally circular cross-section and noapparent skin-core structure. It will have a minimum wet strength of 2.2grams per denier and a wet modulus of above 1 gram per denier at 5%extension. The wet modulus is the stress in grams per denier required toattain a given extension of fiber saturated with water.

Rayons other than polynosique rayon are preferably not used in thepresent process except in blends with at least natural cellulose orpolynosique rayon fibers. When treated with 5 to 40% NaOH, conventionalrayons tend to be gelatinized, so that when the yarn contains more thanabout 35% of such fiber the finalproduct. is

stiff, boardy and unmerchantable.

Yarns employed in the present invention may also include a minorproportion of non-cellulosic fibers, provided, however, that such fibersdo not aifect the basic nature of the blend.

The singles yarns used in the plied yarn may be of any desired weight orconstruction varying from about 1 denier to about 15 denier. They may betwisted in either direction, and to any desired extent. The twist inthecomponent singles yarns, should, however, be opposite 'in direction tothe ply twist. Normally the singles yarns will have 10 to 40 turns perinch and the ply 5 to 40.turns per inch in the opposite direction.

The swelling agent used is an aqueous solution equiva ent in swellingpower to solutions containing 5 to..40% by weight NaOH. Preferably thesolution will in fact be a solution of 5 to 40% NaOH and most preferably3 5 to NaOH. Other swelling agents may be used, if desired, includingother alkali metal hydroxidees such as KOH and such materials as zincchloride and sodium zincate.

The temperature at which the swelling agent is applied may be variedconsiderably. In accordance with well known principles, lowertemperatures tend to cause a more vigorous swelling action.Conveniently, the treatment is carried out at room temperature (20 C.,more or less) but may be carried out at any temperature between thefreezing and boiling points of the solution.

The time of treatment will vary depending on the nature andconcentration of the swelling agent and on the nature of the fiber, onthe mechanical construction of the yarn and on mechanical details of thetreating apparatus. Broadly, it may range from say .1 to 120 minutes.

The physical arrangements for treating the yarn may vary widely. Incommercial practice a conventional warp mercerizing machine may beemployed. In laboratory or small scale operations, the yarn may bewrapped on a form or bobbin of suitable size and shape, the yarn beingwrapped in such a manner that when it undergoes shrinkage duringtreatment, it will conform to the out ine of the form or bobbin and thusreach the desired proportion of its original length and so be subjectedto the appropriate tension. The treating liquor may be applied bydipping, spraying or in any other convenient way.

Following contact with the swelling agent the yarn is washed,neutralized with a weak acid such as acetic acid, and dried. These stepsare carried out with the yarn under tension.

In accordance with the invention, the yarn is then reverse twisted,i.e., it is given a twist in a direction opposite to that in which itwas plied. While the degree of reverse twist may vary, preferably it isbetween about 135 and 160% of the initial ply twist. The result is shownclearly in FIG. 3. As can be seen from that figure, the yarn is now anirregular three dimensional sequence of helical sections, the helixangle of succeeding sections varying in an arbitrary and random manner.The yarn is stretchy and when extended and released will recover itsoriginal length to a high degree.

It is difficult to process stretch yarn, as such, on looms and knittingmachines, precisely because it is stretch yarn. However, this is not aproblem with the present yarn because when the yarn is wound on a spool,preparatory to heir: converted into fabric, the tension incident towinding pulls the stretch out. If maintained under tension in theextended position for more than about minutes, the yarn loses itsrecovery ability substantially entirely. Normally, the yarn stays woundon a spool for at least 24 hours before it is used and in this time theyarn loses its apparent stretchability. It can thus be woven or knittedjust as though it had never had stretch characteristics. When, however,the resulting fabric is wetted, or steamed, under zero tension, thestretch characteristics redevelop and the result is a? stretch fabricmade of 100% cellulose.

The invention is illustrated in the following examples.

Example I Samples of a 24/2 (5.5 t.p.m.) high wet modulus rayon yarnhaving a wet modulus of 2 grams per denier at 5% extension are wrappedon plastic forms in such a way that when shrunk to conform to the formsthey have lengths 70, 80, 90, 95 and 100% of the original length. Theyare then treated with 16% aqueous NaOH for 2 minutes. All samples shrinkto fit closely over the forms. The samples are washed with water,neutralized with 5% acetic acid, washed with water and dried on theforms. They are then removed from the forms and reversetwisted to 31.8turns per inch. Samples of the reverse twisted yarn are then relaxed inwater for five minutes at 65 C. and dried. Recovery values aredetermined by stretching the yarns along a calibrated scale to 4 maximumusable stretch, keeping the 'ya'rns' 'afth'a't'point for five minutesand then relaxing for one minute before noting the return length. Theresults are as follows:

TABLE Length of sample After Treatment Maximum Usable Percent Sample(percent at Stretch (percent) Recovery original length) In theseresults, percent recovery is calculated as follows:

percent stl eteh percent growth X100 Percent rewverypercent stretchwhere length after stretch and relewe-origlnal length original lengthExample II The procedure of Example I is followed using a 30/2 cottonyarn and 25% NaOH. Like results are obtained.

Percent stretch:

Example 111 The yarn made according to Example I (Sample A) is wound onspools. In this procedure substantially stretch is removed from theyarn, though this can easily be redeveloped by wetting or steaming.Several days after winding, the yarn is knitted into a fabric which isrelaxed in water at 60 C. for five minutes. It has excellent stretch andrecovery characteristics.

What is claimed is:

1. A method for making a stretchy yarn which comprises contacting acellulosse yarn having at least 2 plies with a cellulose swelling agentequivalent to an aqueous solution containing 5 to 40% sodium hydroxideand capable of shrinking said yarn, maintaining said yarn during contactwith said swelling agent under a tension sufiicient to maintain saidyarn at least 50% of its original length and subsequently reversetwisting the treated yarn in a direction opposite to the initial plytwist and to a degree greater than the initial ply twist.

2. The method claimed in claim 1 wherein the cellulose yarn comprisesfilaments selected from the group consisting of cotton, and rayon havinga wet modulus greater than about 1 gram per denier at 5% extension.

3. A method for making a stretch yarn which comprises treating a pliedyarn consisting essentially of filaments selected from the groupconsisting of cotton, and rayon having a wet modulus greater than about1 gram per denier tt 5% extension, with an aqueous solution con taining5 to 40% by weight NaOH at a temperature between about 0 and about 80C., for between about 0.1 and about minutes, and maintaining said yarnduring contact with said solution at a length between 50% and 100% ofits original length, and subsequently reverse twisting the treated yarnin a direction opposite to the initial ply twist and to a degree greaterthan the initial ply twist.

4. A method for making a stretch fabric which comprises treating amulti-ply yarn consisting essentially of cellulose filaments with aswelling agent for cellulose equivalent to an aqueous solutioncontaining between about 5 and about 40% NaOH, under a tensionsufficient to maintain said yarn at not less than 50% of its untreatedlength, reverse twisting the yarn in a direction opposite to the initialply twist and to a degree greater than the initial ply twist, convertingthe yarn to a fabric and relaxing the fabric in an aqueous fluid.

5. The method claimed in claim 4 wherein the cellulose is naturalcellulose.

6. The method claimed in claim 4 wherein the cellulose is rayon having awet modulus greater than about 1 gram per denier at 5% extension.

References Cited UNITED STATES PATENTS 2,254,740 9/1941 Hansen et al57-139 2,463,618 3/1949 Heberlein et'al 57-157 2,895,287 7/1959 Yoo57164 2.895388 7/1959 Yoo 57-164 1,820,663 8/1931 Holt 28--76 FOREIGNPATENTS 501,833 1939 Great Britain.

OTHER REFERENCES American Cotton Handbook, edition 1941, pages 654- 657,published American Cotton Handbook Co.

Some Fundamentals of Stretch Cottons, E. S. Olson, vol. 52, Sept. 2,1963, pages 21-8, 52.

LOUIS K. RIMRODT, Primary Examiner.

1. A METHOD FOR MAKING A STRETCHY YARN WHICH COMPRISES CONTACTING ACELLULOSE YARN HAVING AT LEAST 2 PLIES WITH A CELLULOSE SWELLING AGENTEQUIVALENT TO AN AQUEOUS SOLUTION CONTAINING 5 TO 40% SODIUM HYDROXIDEAND CAPABLE OF SHRINKING SAID YARN, MAINTAINING SAID YARN DURING CONTACTWITH SAID SWELLING AGENT UNDER A TENSION SUFFICIENT TO MAINTAIN SAIDYARN AT LEAST 50% OF ITS ORIGINAL